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Coverage Planning and Resource Allocation in Broadband Cellular Access: Optimization Models and Algorithms
Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology. (Communications and Transport Systems)
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The last two decades have witnessed a booming in the use of cellular communication technologies. Billions of people are now enjoying the benefits of mobile communications. This thesis deals with planning and optimization of broadband cellular access network design and operation. The problem types considered include coverage planning, power optimization, and channel assignment. Mathematical modeling and optimization methods have been used to approach the problems.

Coverage planning is a classical problem in cellular network deployment. A minimum-power covering problem with overlap constraints between cell pairs is considered. The objective is to minimize the total power consumption for coverage, while maintaining a necessary level of overlap to facilitate handover. For this coverage planning problem, the thesis develops two integer programming models and compares the models' strength in approaching global optimality. In addition, a tabu search algorithm has been developed for solving the problem in large-scale networks.

For High Speed Downlink Packet Access (HSDPA) networks, transmission power is a crucial factor to performance. Minimizing the power allocated for coverage enables significant power saving that can be used for HSDPA data transmission, thus enhancing the HSDPA performance. Exploring this potential power saving, a mathematical model targeting cell-edge HSDPA performance has been developed. In determining the optimal coverage pattern for maximizing power saving, the model also allows for controlling the degree of soft handover for Universal Mobile Telecommunications System (UMTS) Release 99 services. In addition to the mathematical model, heuristic algorithms based on local search and repeated local search are developed.

For Orthogonal Frequency Division Multiple Access (OFDMA), which is used in Long Term Evolution (LTE) networks, inter-cell interference control is a key performance engineering issue. The aspect is of particular importance to cell-edge throughput. Frequency reuse schemes for mitigating inter-cell interference at cell-edge areas have received an increasing amount of research attention. In the thesis, a generalization of the standard Fractional Frequency Reuse (FFR) scheme is introduced. The generalization addresses OFDMA networks with irregular cell layout.  Optimization algorithms using local search have been proposed to find the frequency reuse pattern of generalized FFR that maximizes the cell-edge area performance.

For the problems considered in the thesis, computational experiments of the optimization models and algorithms using data sets representing realistic planning scenarios have been carried out. The experimental results demonstrate the effectiveness of the proposed solution approaches.

Place, publisher, year, edition, pages
Norrköping: Linköping University Electronic Press , 2010. , 21 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1454
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-62764Local ID: LIU-TEK-LIC-2010:25ISBN: 978-91-7393-279-0 (print)OAI: oai:DiVA.org:liu-62764DiVA: diva2:374219
Presentation
2010-12-17, K3, Kåkenhus, Campus Valla, Linköpings university, Norrköpinf, 13:15 (English)
Opponent
Supervisors
Available from: 2010-12-30 Created: 2010-12-03 Last updated: 2010-12-30Bibliographically approved
List of papers
1. Solving a minimum-power covering problem with overlap constraint for cellular network design
Open this publication in new window or tab >>Solving a minimum-power covering problem with overlap constraint for cellular network design
2010 (English)In: European Journal of Operational Research, ISSN 0377-2217, E-ISSN 1872-6860, Vol. 203, no 3, 714-723 p.Article in journal (Refereed) Published
Abstract [en]

We consider a type of covering problem in cellular networks. Given the locations of base stations, the problem amounts to determining cell coverage at minimum cost in terms of the power usage. Overlap between adjacent cells is required in order to support handover. The problem we consider is NP-hard. We present integer linear models and study the strengths of their continuous relaxations. Preprocessing is used to reduce problem size and tighten the models. Moreover, we design a tabu search algorithm for finding near-optimal solutions effectively and time-efficiently. We report computational results for both synthesized instances and networks originating from real planning scenarios. The results show that one of the integer models leads to tight bounds, and the tabu search algorithm generates high-quality solutions for large instances in short computing time.

Keyword
OR in telecommunications; Cellular networks; Covering; Integer programming; Tabu search
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-52895 (URN)10.1016/j.ejor.2009.09.018 (DOI)
Note
Original Publication: Lei Chen and Di Yuan, Solving a minimum-power covering problem with overlap constraint for cellular network design, 2010, European Journal of Operational Research, (203), 3, 714-723. http://dx.doi.org/10.1016/j.ejor.2009.09.018 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/Available from: 2010-01-13 Created: 2010-01-12 Last updated: 2017-12-12
2. Coverage Planning for Optimizing HSDPA Performance and Controlling R99 Soft Handover
Open this publication in new window or tab >>Coverage Planning for Optimizing HSDPA Performance and Controlling R99 Soft Handover
2012 (English)In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 51, no 1, 53-64 p.Article in journal (Refereed) Published
Abstract [en]

Coverage planning is an important engineering task in deploying UMTSnetworks implementing both high speed downlink packet access (HSDPA)and Release 99 (R99) services.  Coverage planning amounts todetermining the cell coverage pattern by means of setting the commonpilot channel (CPICH) power of the cells. A conventional strategy isto uniformly allocate a proportion of the total power to CPICH. Inthis paper, we develop mathematical modeling and optimizationapproaches to bring the benefit of power saving enabled by optimizingnon-uniform CPICH to enhance HSDPA performance, while preserving adesired degree of soft handover (SHO) for R99.  The studyfocuses on HSDPA performance at cell edges, where data throughput istypically low.  An integer linear programming model is developed forthe resulting optimization problem.  The model admits optimal ornear-optimal planning solutions for relatively small networks.Solution algorithms based on local search and repeated localsearch are developed.  These algorithms are able to perform theoptimization for large-scale networks time-efficiently.  Experimentalresults for both synthesized networks as well as instances originatingfrom real planning scenarios demonstrate the benefit of ouroptimization approach.

Place, publisher, year, edition, pages
Springer, 2012
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-62761 (URN)10.1007/s11235-010-9414-z (DOI)000311517300006 ()
Note

funding agencies|CENIIT||Linkoping Institute of Technology, Sweden||Swedish Research Council (Vetenskapsradet)||ELLIIT network||

Available from: 2010-12-03 Created: 2010-12-03 Last updated: 2017-12-12
3. Generalizing and Optimizing Fractional Frequency Reuse in Broadband Cellular Radio Access Networks
Open this publication in new window or tab >>Generalizing and Optimizing Fractional Frequency Reuse in Broadband Cellular Radio Access Networks
2012 (English)In: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499, Vol. 230Article in journal (Refereed) Published
Abstract [en]

For broadband cellular access based on orthogonal frequency divisionmultiple access (OFDMA), fractional frequency reuse (FFR) is one ofthe key concepts for mitigating inter-cell interference and therebyoptimizing cell-edge performance. In standard FFR, the number of OFDMAsub-bands and the reuse factor are both fixed. Whereas this works wellfor an idealized cell pattern, it is neither directly applicable noradequate for real-life networks with very irregular cell layouts. Inthis paper, we generalize the standard FFR to allow for flexibilities inthe total number of sub-bands as well as the number of sub-bands ineach cell-edge zone, enabling network-adaptive FFR. Two powerassignment strategies that use fixed power per sub-band prior tosub-band allocation and apply cell-specific power derived from thenumber of sub-bands allocated to each cell-edge zone, respectively,are investigated. Optimization algorithms based on local search aredeveloped for sub-band allocation to maximize the cell-edgethroughput. Evaluations using networks with realistic radiopropagation conditions demonstrate the applicability of the generalizedand optimized FFR in performance engineering of OFDMA networks.

Keyword
orthogonal frequency division multiple access; fractional frequency reuse; optimization; local search.
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-62762 (URN)10.1186/1687-1499-2012-230 (DOI)000315038300001 ()
Available from: 2010-12-03 Created: 2010-12-03 Last updated: 2017-12-12Bibliographically approved

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